Free tool · works now
YAML Frontmatter Validator
Validate, lint, and normalize Markdown YAML frontmatter blocks against Obsidian and static site generator standards.
Runs 100% in your browser. Paste your Markdown note to validate frontmatter syntax, detect illegal tabs, verify ISO dates, and prevent parser crashes.
✓ No syntax issues found. --- title: "Quarterly Systems Architecture Review" date: 2026-10-09 category: Engineering tags: - architecture - macos - audio-pipeline attendees: - "Marcus Chen" - "Elena Vance" status: published summary: "Detailed review of on-device Whisper transcription latency and CoreAudio loopback performance." related_notes: - "[[Obsidian Audio Workflow]]" - "[[ScreenCaptureKit Deep Dive]]" ---
Why strict YAML frontmatter validation is essential
YAML frontmatter is the standard mechanism for attaching structured metadata to plain Markdown documents. Static site generators such as Astro, Hugo, and Jekyll, as well as personal knowledge management applications like Obsidian and Foam, rely on YAML headers bounded by triple dashes (---) to catalog tags, publishing dates, author attributions, and document statuses. However, because YAML is an indentation-sensitive specification with strict grammatical rules, small formatting mistakes frequently cause complete build failures or silent indexing omissions.
A single tab character accidentally inserted into a frontmatter block violates the YAML specification and causes standard parsers (including PyYAML, js-yaml, and libyaml) to abort execution. Similarly, writing an unquoted wikilink such as related: [[Meeting Agenda]] tricks the parser into expecting a flow-style nested array, resulting in unexpected token errors. Validating your frontmatter before running automated publish pipelines prevents broken builds and maintains the integrity of your personal knowledge graph.
Common frontmatter syntax pitfalls detected by this tool
Our browser-based validator performs a comprehensive series of linting checks across every line of your frontmatter block:
- Illegal tab characters: Identifies tab indentation and advises replacing tabs with standard 2-space increments to ensure cross-platform compatibility.
- Unbalanced quotation marks: Flags missing closing single or double quotes in string properties that cause multiline parsing freezes.
- Colon spacing violations: Enforces standard
key: valuesyntax by flagging instances where a space was omitted after the colon separator. - Unquoted wikilink sequences: Detects unquoted double brackets and recommends wrapping references in quotes (e.g.
"[[Note Title]]") to satisfy strict YAML parsers while allowing Obsidian link indexing. - ISO 8601 date validation: Verifies that dates assigned to
date,created, andupdatedproperties follow the standardYYYY-MM-DDor full ISO timestamp format.
Zero network transmission for private note properties
Personal notes and executive meeting logs frequently contain confidential project codenames, client identifiers, and organizational hierarchy tags within their frontmatter blocks. Uploading those notes to third-party web validators creates unacceptable security exposures. This validator executes entirely within your browser tab using zero external APIs or third-party servers.
In Oyma, frontmatter metadata is preserved verbatim on disk alongside your plain text notes. We believe your notes should never be locked inside a closed database. Explore our local full-text search engine and learn how our Obsidian vault architecture keeps your knowledge private and durable.
Frequently asked questions
Questions
Why does YAML prohibit tab characters for indentation?
The official YAML 1.2 specification strictly forbids tab characters for structural indentation because different text editors and terminal environments render tabs with inconsistent column widths (varying from 2 to 8 spaces). Using spaces guarantees deterministic hierarchy across all parsers.
Why do wikilinks inside frontmatter need quotation marks?
In standard YAML syntax, double square brackets [[...]] denote a nested flow sequence (a list of lists). If you write a wikilink without quotes like related: [[Note Name]], standard parsers throw a fatal syntax error. Wrapping it in quotes ("[[Note Name]]") preserves the string literal.
What is the required format for frontmatter dates?
Obsidian, Astro, and most static site generators require dates in ISO 8601 format (YYYY-MM-DD or YYYY-MM-DDTHH:MM:SSZ). Malformed dates cause indexing failures in Dataview queries and static site compilation pipelines.
Does this tool transmit my private note metadata anywhere?
No. The validation logic runs entirely in your browser memory via client-side JavaScript. No note metadata, tags, titles, or properties are sent over the network.
How does the desktop app handle note frontmatter?
The desktop app natively supports YAML frontmatter properties, allowing you to edit metadata with interactive tags, dates, and aliases while keeping the underlying Markdown file completely clean on your local disk.
Looking for private, local Markdown notes on your Mac?
Organize your thoughts, daily notes, and meeting records in plain Markdown with zero cloud telemetry in Oyma.